Musnad Abu Ya'la al-Mawsili 155:156

And from Abu Salamah, he said: I saw Abu Hurairah prostrate during "When the sky has split asunder" (Surah Al-Inshiqaq). I said: "O Abu Hurairah, I see you prostrating during 'When the sky has split asunder'?" He said: "Had I not seen the Messenger of Allah, may Allah bless him and grant him peace, prostrate during it, I would not have prostrated."